The United States produces about 20 trillion scf/year of natural gas that generates more than $100 billion annually in sales and provides crucially needed energy resources. According to the most recent International Energy Outlook, natural gas is the fastest growing energy source and worldwide consumption is expected to increase 92% by 2030. However, nearly all natural gas requires some type of treatment to reduce contaminants. The most abundant contaminant, carbon dioxide (CO2), has typical concentrations between 5-25 mol %, while some reservoirs contain levels even above 50%. In order to meet pipeline specifications for transport and to minimize pipeline corrosion, the carbon dioxide concentration must be reduced to less than about 2%. Other applications within the natural gas industry involving the removal of carbon dioxide include recovery and recycling of carbon dioxide in enhanced oil/gas recovery, recovery of methane from landfills and biogas, and recovery of carbon dioxide from flue gases. Membrane-based separation processes offer an attractive alternative to traditional absorption processes due to their relatively low capital and operational costs, portability, scalability, and environmental security.
Membranes are relatively simple devices that can act effectively as “molecular filters” for gas molecules. More fundamentally, gas transport through a polymer medium occurs through a combined mechanism known as “solution-diffusion.” A penetrant from a feed stream sorbs at the surface of the upstream side of the membrane and then diffuses through the membrane film to the downstream surface where it desorbs into the permeate stream. The driving force for this process is related to the change in partial pressure or fugacity of a penetrant between the feed and permeate streams.
To complicate matters, strongly sorbing species, such as CO2, swell polymer membranes and cause “plasticization” of the membrane, which refers to an increase in permeability due to enhanced polymer segmental mobility. This increased local segmental mobility reduces the size and shape of the discriminating capabilities of the polymer, thereby undermining the separation efficiency of the membrane.
Accordingly, there is a need for thermally crosslinked polymeric compositions and methods of making the same to reduce CO2-based, swelling-induced plasticization of membranes. It is to the provision of such thermally crosslinked polymeric compositions and methods of making the same that the various embodiments of the present invention are directed.